Device for breaking up the cores formed by core drills



$- GSTALDER ET AL Filed March 16, 1967 DEVICE FOR BREAKING UP THE CORESFORMED BY CORE DRILLS May 13, 1969 R MM o .AN 2 WGRRM 0 7 3 2 I w. z z 47 //W/// \\\\\\\M \\\\\\\\\\\\\\\\\\\m M w I fill? II II M WT Z 1 on;Aha-nus United States Patent 01 fice Int. Cl. E21b 9716,- E21c 13/02U.S. Cl. 175-404 Claims ABSTRACT OF THE DISCLOSURE A core drillcomprising means for breaking up the core as it is formed whichcomprises a system for applying hydraulic pressure to the core-breakingmember and regulating the pressure thus applied by controlling the dropin drilling fluid pressure across the tool.

SPECIFICATION The present invention relates to a hydropneumatic tool fordestroying the cores formed during the drilling of a well. It is anestablished practice to use drilling tools which cut out the rock orground within an annular space while leaving the rock or ground insidethat space intact, and this remainder is commonly referred to as thecore. Related tools have been used to recover the cores, which are forpractical purposes specimens of the formation being drilled.

It is also conventional to use core cutting tools provided with meansfor destroying the core. Such tools may be used for drilling. Theypermit an increase in the effective drilling speed because thedestruction of the rock is directly related, especially in the case ofdiamond headed tools, to the linear speed of displacement of thediamonds in contact with the rock. It is well known to use for thisdestruction tools comprising a punch fixed to the core drill and eitherstationary or rotatable about an axis which may be, but is notnecessarily parallel to the drilling axis. This punch may turn freelyabout its axis, and since it is fixed to the tool the reaction of thecore-cutting tool against the punch reduces the effective weight appliedto the head of the core drill. It is well known that an increase in'thespeed at which these tools make hole is dependent on the section andhardness of the core, and that the larger the section the greater theforce required to break it up.

An adequate length of life for the punch and an increase in the maximumdrilling speed are provided by holding the punch stationary with respectto the core, that is, so that it rotates with respect to the tool. Along length of life is insured by the positions of the thrust bearings.The best results stem from the use of a bearing in which the effectiveforces exerted against the bearing surfaces are minimal. Thus for abearing having a given diameter (which is determined by the spaceavailable), the working life of the tool is increased and the diameterof the core is increased to a maximum. It is also known that drillingtools having bearings must be lubricated in order to prolong theiruseful life as long as possible.

These advantages which are of proven commercial value, have beenattained by the tool according to the present invention.

In accordance with this invention, the core-destroying device comprisesa punch which is free to rotate about an axis parallel to the drillingaxis, said punch being sub jected to hydraulic pressure through achamber filled with an incompressible liquid, said chamber being formedto receive at its upper end a piston having a smaller section at itslower end than at its upper end. This piston thus serves as a pressuremultiplier, when an easily compressed fluid is used in the intermediatechamber.

In accordance with one feature of the invention, the shaft carrying thepunch is mounted inside a chamber of predetermined dimensions by meansof an arrangement which permits it to rotate, said arrangementpreferably comprising a set of roller bearings and tapered rollerbearings so assembled that the average force exerted against the bearingraces is very low.

In accordance with another feature of the invention the upper pistonmoves in a chamber having two different sections, the section of thelower part being less than or equal to the total surface of the upperpart. The lower part of the piston slides in this chamber having twoparts thereby defining an intermediate chamber.

In accordance with yet another feature of the present invention, thecompressible fluid enclosed in the intermediate chamber is a gas, suchas air, nitrogen, or any other suitable gas. A final feature is that thedevice embodying the invention is attached to the drilling tool by ascrew threaded joint provided with sealing means, so that it may be usedwith any drilling tool.

In order that the invention may be more clearly understood, severalembodiments thereof will now be described purely by way of example, withreference to the accompanying drawing, in which:

The figure represents an embodiment of the apparatus according to theinvention in which the punch-carrying piston is rotatably mounted in aset of thrust bearings.

Reference numeral 1 indicates the threading by which the device may beattached to a diamond bit, a core drill or any other appropriate tool(not shown).

Reference numeral 2 indicates the body of the device, which may beattached by a second set of threads 3 to a string of pipes and/0rcollars as is conventional in drilling oil wells for example. The body 2is formed from the two parts 4 and 5, which may be screwed or weldedtogether.

The part 4 is provided at its lower end with one or more openings 6through which debris resulting from the destruction of the core may beevacuated.

The punch 7 is fixed to the shaft 8 which is free to rotate about theaxis 9, and turns freely in the roller bearings 10, and the taperedthrust bearings 11. This shaft is subjected to reactive pressure fromthe core 12, which fractures under the pressure of the punch along linessuch as those indicated at 13. This shaft is also subjected to thehydraulic pressure of an incompressible fluid positioned in the chamber14. The fluid in the chamber 16 is acted upon by an intermediate piston15 which is itself subjected to the pressure of the fluid in the chamber16, which is compressed by the upper piston 17, the upper surface 18 ofwhich is subjected to the pressure of the drilling fluid and isresponsive to the pressure differential through the tool created bywhatever system is in use.

The chamber 20 is filled with compressed air, which results in pressuremultiplication bythe cylinder 17.

In order to provide a more convenient mounting for the :bearing racesfor the punchcarrying piston, the intermediate rings 21 and 22 aremounted inside the body 4, which permits the sealing rings such as 23 tobe very fluid-tight. The sealing rings 24 are mounted on the piston 17so as to insure efifective sealing in of the gas.

The operation of this system may be described as follows: Assuming thepressure of the drilling fluid on the surface 18 to be P the pressure inthe chamber 16 is P XS/s, if S and s are the upper and lower surfaces ofthe piston 17.

All of this pressure is exerted on the shaft 8 and Patented May 13,1969. I

through said shaft there is exerted on the punch a force in which P isthe pressure of the drilling fluid under the punch and a the section onwhich the pressures act. It will thus be seen that by creating arelatively small pressure difference P P through the tool a relativelyhydraulic force is provided.

When the core punch according to the invention contacts the core, thereactive force exerted on the punch increases as the core drill advancesinto the ground. This force increases until it reaches the valuerequired to break up the core.

In the absence of hydraulic pressure this reactive force is resisted bya plain thrust bearing. Thanks to the presence of hydraulic pressure,the value P of which is regulated so that it equals half the pressurerequired to break up the core, a double-acting thrust bearing is usedwhich makes it possible for each element of the bearing to operate underhalf the load of a plain bearing, and the working time of each bearingis likewise divided by two. In this case the bearing lasts about fourtimes as long as a plain bearing.

This improvement is obtained only when hydraulic pressure is present.The component parts are separate from each other, which permits aminimum operating cost. The advantages of such an arrangement areobvious, since it permits the cutting heads of the core drills to beinterchanged when the diamonds or cones are Worn. This makes it possibleto salvage the device according to the invention and reuse it with a newhead.

In a particular embodiment of the invention the piston 17 is providedwith a concentric piston 25, of relatively small diameter, which isfreely slidable and provided with a shoulder at its upper end.

In the normal operation of the apparatus this piston 25 (FIG. 1) remainsstationary, being held against the shoulder by the pressure exerted onits lower face. This pressure is applied to the punch-carrying shaftthrough a fluid such as a grease.

If a leakage of the fluid results, the piston 17 is forced to the bottomof the chamber 20, and at this moment the piston 25 leaves its seat sothat the pressure of the fluid in the passage 19 may be applied directlyto the piston 15.

Leakage is held to a minimum by means of sealing rings and labyrinths.

What is claimed is:

1. Core-breaking means for use in combination with a core drill adaptedto cut a core from material into which it is driven and comprising afluid pressure system which develops a pressure drop across said drillwhen it is being operated, together with means for regulating said drop,said core-breaking means comprising a punch mounted for rotatable andaxial movement within said drill with its lower end positioned to engagea core in said drill, and a transfer system for applying to said punch apressure derived from said pressure drop, said transfer systemcomprising a pressure multiplied for multiplying the pressure from saidfluid pressure system applied to said punch.

2. Apparatus as claimed in claim 1 in which said punch is mounted inthrust bearings and the fluid pressure applied to said punch is soapplied as to at least partially counterbalance the load resulting fromthe pressure of said punch on said core, thereby reducing the load onsaid thrust bearings.

3. Apparatus as claimed in claim 1 in which said transfer systemcomprises a free piston interposed between said punch and the fluidpressure system which develops said pressure drop.

4. Core-breaking means as claimed in claim 1 in which said pressuremultiplier comprises a piston having a pres sure receiving facesubjected to pressure from said fluid pressure system and a pressureexerting face having substantially the same total area, saidpressure-exerting face being divided into a first portion which acts ona chamber containing a compressible fluid and a second portion whichtransmits pressure to said punch through a relatively incompressiblefluid.

S. -In a core drill adapted to cut a core from material into which it isdriven and comprising a fluid pressure system which develops a pressuredrop across said drill when it is being operated, together with meansfor regulating said drop, the improved core-breaking means whichcomprises a punch mounted for rotatable and axial movement within saiddrill with its lower end positioned to engage a core in said drill, anda transfer system for applying to said punch a pressure derived fromsaid pressure drop, said transfer system comprising a pressuremultiplier in said transfer system for multiplying the pressure fromsaid fluid pressure system applied to said punch.

References Cited UNITED STATES PATENTS 1,660,201 2/1928 Lee -922,345,024 3/1944 Bannister 175-92 X 2,868,511 1/1959 Barrett 175-333 X2,873,093 2/ 1959 Hildebrandt 17592 3,130,799 4/1964 Williams 175-923,219,131 11/1965 Boyd 175404 N-ILES C. BYERS, JR., Primary Examiner.

